Open the control panel then click on Administrative Tools then Computer Managment, then Device manager and see if there are any yellow circles beside any devices. If there are update the drivers for them by right clicking on the affected device and chose Update Driver.
As you have not said any differently I take it that you are connecting via USB to the Net. There are a couple of problems with this form of Internet connection as firstly it is slower than it can be and the bigger problem is that it is no where near as reliable as an Ethernet connection. If you have a Ethernet socket on your Modem use a CAT 5 Cable to connect the modem to the computer in the On Board LAN that will result in a more reliable connection. If you already have the LAN in use you'll need to fit another NIC to the computer in one of the 2 PCI expansion slots you'll need a 10/100 TBase type NIC as the Gigabite Card will not work with the already installed 10/100 LAN connection.
Col